Miniature incandescent lamp



June 24, 1941. J. E. WITBECK MINIATURE INCANDESCENT LAMP Filed April 15, 1939 IN VENTOR Jean E. Wz'ibeck Patented June 24, 1941 MINIATURE. INCANDESCENT LAMP" Jean E. Witbeck, Nutley, N. J., assignor to Tung Sol Lamp Works, 1110., Newark, N. J a corporation of Delaware.

Application April 13, 1939, Serial No; 267,541

Claims.

This invention relates to electric incandescent lamps and to the manufacture thereof.

In the manufacture. of filament 'mounts' for miniature incandescent lamps, the tungsten filament .1egs,;and. particularly the minor or small filament of'multi-filament'bulbs,are often impaired or weakened .bythe welding operations and'the reheating thereof in service. The weldingxor fastening in conventional practice is effected by positioninghthefilament leg or end crosswise'of thenickelwireand then with one of the relatively movable electric welding electrodes in direct engagement with the filament leg the latter is pressed on and welded to the nickel wire simultaneously with the supply of electric heating current between the electrodes. Conventional lamp structures of filaments thus welded. often prematurely fail and do not stand up under :serviceconditions. These :failures are probably-due to the high temperatures to which the tungsten filament terminal is brought during the welding operation. whereby its strength is impaired by the disturbance or upsetting of its crystalline structure, with the result that when reheating at thejweakenedpoints while the lamps arein-use thefilamentsfailby breakage at these points.-

I have foundthat thesepremature failures of by the welding operations by so constructing the filament mount that 'the filament legs at the weakenedspoints are kept cool and the reheating thereof' to the breaking points avoided in the use of the bulb.

For a better understanding. of-the invention reference maybe had to the accompanying drawing forming a part b of {this application, wherein Figs..1A and'lB are views'of filament mounts embodying the invention; 1

Fig. 2 is a perspective View of a two-filament miniature incandescentlamp bulb embodying the invention;

Fig. :3 is an end view thereof with-certain parts broken. away; and

Fig.= 4 is a view showing a modified minor filament mount embodying the invention.

Referring to Figs. 1A and 1B of'the drawing; the invention is illustrated as embodied in a filament mount comprising the nickel support Wires 4 and 1 and the filament 8. The main body or light giving part of the filament is in the conventional coiled or helix form and is provided with integral elongated filament legs or terminals 8' which are formed of straightnon-colled'wire,

Theseterminals are carried or bent at least part way around the filament support wires 4 and 7 and in close proximity thereto and are electrically welded at the points 9 and HI respectively'to the' wires 4 an; As describedabove, the filament legs 8' are brought toa very high temperature during the electrical welding andfastening operations at the points 9 and :lllfand the conventional mounts often fail" in service due cto'the' breakage of the filament legs 8 at the' points 9 and It or at points adjacent' thereto. I have found however, that by carrying and'bending the legs 8" of the filamentat least partway around the support wires 4 and I andbringing'thelegs for a considerable distance in advance of the welding points 9 and 10 into close proximity-to the support wires 4 and 1 these failure are obviated-or are substantially reduced. Apparently the support wires 4 and I exert a very substantial cooling effect upon the weakened part of the filament legs 8"with the' result that the temperatures thereof-are kept below those values at which the filament-legs would rupture or break in use. The preferredconstruction isindicated' in Fig. 1A wherein-the filament legs 8' are in both electricaland heat conducting relatlon with the support wires 4and 1 for a considerable portion of the lengths whereby the weakened points of the legs 8' are short-circuited in use with' the resultthat the legs are kept cool bothbythe elimination of the heating current passing therethrough and by the rapid conductance of heat to the support wires 4 and- 1 Even in the mount of Fig, 13; however; wherein no'substantial part of either of the filament legs 8 is short-circuited, the cooling efiect of the support wires '4 and 1 upon the closely disposed filament legs 8' throughout the weakened portion there'ofis sufficient to avoid the rupture or breakage in practice.

Referring to Figs. 2 and 3 of the drawing, the inventionis illustrated as embodied in a twofilament miniature incandescent lamp bulb comprising. a glass envelope I, a base 2, and a glass press 3.. The glass press carries a pair-of nickel support wires 4 and 5 upon which is mounted the. major filament 6; A third nickel support wire I is mounted on the press 3 and a minor filament 8 is mountedon the nickel wires 4 and 1. The minor filament has legs or terminals 3. which are somewhat elongated and are electrically welded in the conventional manner to the nickel support wires4 and 1 at the points 9 and II), respectively. It is observedthat these points of weldor fastening 9 and 'lllaredisposedon the opposite sides .of the'nickel support wires from the body or coiled portion of the filament and out of the plane of the body portion of the filament, with the result that between the weld points 9 and I9 and the body portion of the filament the filament legs 8' are wound partly about the support wires so as to be in close proximity to and in heat conducting relation with the nickel support wires at points in advance of the weld points, and preferably in electrical contact with the supports 4 and l, as described with respect to Fig. 1A. In the particular embodiment shown these filament terminal portions 8' engage and pass approximately half way around the filament support wires before reaching the welding points 9 and I0.

With this construction and arrangement the filament legs 8 have a substantial portion of their lengths, throughout the weakened points, disposed in close proximity to the support wires 4 and 1 with the resultant cool or low temperature operation and reduction in crystallization and with-the result that the filament failures or breakage. from shock or vibrationis entirely obviated or substantially reduced notwithstanding the conventional electrical welding operation at the points 9 and I9 and'the impairment of the filament leg' structure. Also, as indicated, with this construction and arrangement the heating current passes only through that portion of each of the legs 8' which is adjacent the coiled or body part of the filament and then passes directly into or out of the filament support wires without traversing the whole length of the filament legs 8' and without passing through either the welding points 9 and M or the weakened parts of the-legs adjacent thereto. The reheating at the weakened points is thus obviated notwithstanding the high temperature of the filament body by the heat conducting relation between the terminals 8' and the nickel support wires and by the electrical short-circuiting of the weakened points by the nickel support wires. With the structure shown a part of the mechanical strain is taken up by the terminals 8 passing about the nickel support wires and thus the mechanical strain is removed'in part from the welds 9 and ill, but the absence or reduction of premature failures is due mainlyto'the cool operation of the filament terminals at and adjacent to the welding points 9 and [0.

In the modification of Figs. 2 and 3 the filament 8 is not disposed at right angles to the nickel support wires t and I but is shown as inclined thereto in a somewhat diagonal manner, with the result that the'plane of the filament body 8' is disposed between the weld points 9 and II], that is, the'plane which cuts the support wires and-has the same angular relation with respect to the wires as the filament body, or the plane which cuts the bent portions 8'. In Figs. 1A and 1B the filament is disposed at right angles to the support wires 4 and I and the plane of the filament at right angles to the wires con' tains the welding points 9 and I 0.

In the modification'of Fig. 4 the mount comprises a pair of nickel support wires II and I2 having their outer free ends it and I2 bent outwardly as shown. The minor filament 8 is here disposed at right angles tothe wires H and 12 with the terminals 8 passing part way around the periphery thereof and welded to the bent'ends H and i2 of the support wires at the points 9 and i on'opposite sides thereof from the body portion of the filament 8. Here; as in the thermodifications,the-welding points a a i0 and the portions of the legs or terminals 8' adjacent thereto are in close proximity to and in heat conducting relation with the support wires H and I2 so as to conduct the heat therefrom to the support wires and to keep the same cool. Preferably also the weakened parts of the legs 8 are effectively electrically short-circuited by the terminals engaging the bodies of the support wires II and I2 to avoid heating by the passage of current therethrough. This assures a cool operation of the filament terminals at and adjacent to the welding points 9 and H], with the resultant long useful life desired, notwithstanding the impairment of the filament terminals by the conventional electrical method of fastening.

I claim:

1. In a miniature electric incandescent lamp, a pair of filament support wires, a filament comprising integrally formed a coiled body and noncoiled leg portions, the leg portions being welded to said wires and having parts intermediate the welding points and the body portion which pass at least part way around and in close proximity to the peripheries of the filament support wires.

2. In a miniature electric incandescent lamp, a pair of filament support wires, a filament comprising integrally formed coiled body and. noncoiled leg portions, the leg'portions being welded .to said wires and having parts intermediate the welding points and the body portion which pass at least part way around and in close proximity to the peripheries of the filament support wires, and said legs also engaging said support wires at points in advance of the welding points.

3. In a miniature incandescent electric lamp having a major and a minor filament, a pair of filament support Wires for said minor filament, said minor filament comprising integrally formed coiled body and elongated non-coiled leg portions, said leg portions passing at least part way around and in close proximity to a part of the periphery of the support wires and electrically welded at points adjacent their ends to said support wires.

- 4. In a miniature incandescent electric lamp having a major and a minor filament, a pair of filament support wires for said minor filament;

said minor-filament comprising integrally formed, coiled body and elongated non-coiled leg portions, said leg portions passing at least part way around and in close proximity to a part of the periphery of the support wires and electrically welded at points adjacent their ends to said support wires,

said legs engaging and being in electrical contact with said support wires at points in advance of the welding points.

5. In an incandescent lamp of the character set forth in claim 1 wherein at least one of the filament support wires has a free end bent outwardly away from the filament body, with the non-coiled leg of the filament engaging and passing around a part of the main body of the filament support wire and electrically welded to the outwardly bent portion of the filament support.

7, In an electric incandescent lamp, a pair of V filament support wires, a filament comprising integrally formed body and leg portions, the leg portions being electrically welded to the support wires at points substantially removed from the body portion of the filament and electrically engaging the support wires at points toward the body portion and in advance of the weld points for facilitating heat exchange between the relatively hot leg portions and the relatively cool support wires.

8. In an electric incandescent lamp, a pair of filament support wires, a filament comprising inte y o m d body and leg portions, the leg portions being electrically welded to the support wires at points substantially removed from the body portion of the filament and having parts intermediate the body portion and the weld points in close proximity to and in heat exchange relation with the support wires for facilitating heat exchange between the relatively hot leg portions and the relatively cool support wires.

9. In an electric incandescent lamp, a pair of filament support wires, a filament comprising integrally formed body and leg portions mounted upon said support wires, said leg portions engaging and passing part way around the peripheries of the support wires and welded thereto at points beyond the points where the leg portions engage the support wires for facilitating heat exchange between the relatively hot leg portions and the relatively cool wire supports.

10. In a miniature electric incandescent lamp, a pair of spaced filament support wires and a filament supported by said wires and comprising fastening terminals and a light giving main body, said terminals being bent part way around said wires and electrically welded at points on the peripheries thereof with the bent portions of the terminals disposed in close heat transfer relation to the support wires and between the Weld points and the main body part of the filament.

JEAN E. WI'IBECK. 

